Cigarette smoke filter

Abstract

A novel cigarette smoke filter element is provided which achieves an increased removal of tar from cigarette smoke while retaining a higher flavor level than is achieved using conventional filter materials. The filter comprises an elongate cylinder of microfine fibers which is closed at the upstream end of the filter element and tobacco smoke filter material located both externally and internally of the cylinder of microfine fibers. A tobacco smoke flow path blocking means is provided at the downstream end of the filter element to permit filtered tobacco smoke to pass from the filter element only from the tobacco smoke filter material located internally of the cylinder of microfine fibers.

What we claim is: 
     
       1. A cigarette smoke filter element, comprising: an elongate cylinder of non-absorbent microfine fibers which is closed at the upstream end of the filter element in the intended direction of flow of tobacco smoke through the filter element,   tobacco smoke filter material located both externally of said cylinder of microfine fibers, in the form of an elongate cylinder located between and in engagement with an outer filter element wrapping and the external surface of said elongate cylinder of microfine fibers, and internally of said cylinder of microfine fibers, in the form of an elongate plug in engagement with the inner surface of said elongate cylinder of microfine fibers, and   tobacco smoke flow path blocking means located at the downstream end of said filter element in the intended direction of flow of tobacco smoke through the filter element to permit filtered tobacco smoke having an enhanced flavor-to-tar ratio to pass out of the filter element from radially internally of said elongate cylinder of microfine fibers while inhibiting filtered tobacco smoke from passing out of the filter element from radially externally of said elongate cylinder of microfine fibers.   
     
     
       2. The filter element of claim 1 wherein said tobacco smoke filter material located both externally and internally of said cylinder of microfine fibers is low pressure drop, low filtration efficiency cellulose acetate tow material. 
     
     
       3. The filter element of claim 2 wherein the microfine fibers in said cylinder thereof each has a diameter of about 0.5 to about 10 microns. 
     
     
       4. The filter element of claim 3 wherein said cylinder of microfine fibers has a thickness of about 0.05 to about 4 mm and a density of about 0.05 to about 0.3 g/cc. 
     
     
       5. A cigarette smoke filter element, comprising: an elongate cylinder of non-absorbent microfine fibers each having a diameter of about 0.05 to about 10 microns, said elongate cylinder having a thickness of about 0.05 to about 4 mm and a density of about 0.05 to about 0.3 g/cc and being closed at the upstream end of the filter element in the intended direction of flow of tobacco smoke through the filter element.   tobacco smoke filter material located externally of said cylinder of microfine fibers in the form of an elongate cylinder located between and in engagement with an outer filter element wrapping and the external surface of said elongate cylinder of microfine fibers,   tobacco smoke filter material located internally of said cylinder of microfine fibers in the form of an elongate plug in engagement with the inner surface of said elongate cylinder of microfine fibers, said tobacco smoke filter material located both externally and internally of said cylinder of microfine fibers being low pressure drop, low filtration efficiency cellulose acetate tow material, and   tobacco flow path blocking means located at the downstream end of said filter element in the intended direction of flow of tobacco smoke through the filter element, said tobacco smoke flow path blocking means comprising an annular plate having a diameter corresponding to that of the filter element and a central opening in communication with the downstream end of the tobacco smoke filter material located internally of the cylinder of microfine fibers, to permit filtered tobacco smoke to pass out of the filter element from radially internally of said elongate cylinder of microfine fibers through the central opening.   
     
     
       6. The filter element of claim 4 wherein said smoke path blocking means comprises an outer elongate cylinder of very high density, high pressure drop tow material resistant to tobacco smoke flow therethrough and having an outside diameter corresponding to that of the filter element and an inner elongate cylinder of plastic material bearing against the internal wall of and having the same length as said outer elongate cylinder of very high density, high pressure drop tow material and a central bore communicating with the downstream end of the tobacco smoke filter material located internally of the cylinder of microfine fibers. 
     
     
       7. The filter element of claim 4 wherein said tobacco smoke flow path blocking means comprises an elongate cylinder of very high density, high pressure drop tow material resistant to tobacco smoke flow therethrough and having an external diameter corresponding to that of the filter element and a central bore communicating with the downstream end of the tobacco smoke filter material located internally of the cylinder of microfine fibers. 
     
     
       8. The filter element of claim 4 wherein said tobacco smoke flow path blocking means comprises an elongate cylinder of plastic material and having an external diameter corresponding to that of the filter element and a central bore communicating with the downstream end of the tobacco smoke filter material located internally of the cylinder of microfine fibers. 
     
     
       9. The filter element of claim 1 wherein the tobacco filter material located externally of the cylinder of microfine materials is formed of intermediate density cellulose acetate tow material, the tobacco filter material located internally of the cylinder of microfine fiber is low pressure drop, low filtration efficiency cellulose acetate tow material, and said tobacco filter material located externally of the cylinder of microfine materials also comprise said tobacco smoke flow path blocking means.